Received Date: 30 Jul 2015
Revision Received Date: 31 Aug 2015
Electronic Publication Date: 11 December 2015
This work was supported by the Faculty of Dentistry, Naresuan University (Research grants from income of fiscal year 2014, the grant number: R2557C106). The authors would like to thank Dr. Chalatip Chompunud Na Ayudhya, instructor of Faculty of Dentistry, for valuable discussion and Mr. Arthur John Pollock, instructor of Faculty of Humanities, Naresuan University, for editing the manuscript.